In this work, measurements of U and Ra isotopes in water samples from the Guadalquivir river (Southern Spain) are presented. Uranium and Radium were extracted by using a sequential extraction method. It consisted of a first precipitation of Ba(Ra) sulphate and a subsequent U extraction by using anion exchange resins (Dowex AG1x8 HCI form). Uranium isotopes activities were measured by ion-implanted a spectrometry while radium isotopes were determined by gas flow proportional counting. Levels of U ranged from 1 to 3 µg.l-1 and 234U/238U activities ratios ranged from 1.23 ± 0.11 to 1.38 ± 0.1, while levels from 2 to 20 mBq.l-1 for 226Ra were obtained.